Part 2 of 2

Chart A-7 Fuel System Pressure Test (Part 2 OF 2):

Chart A-7 Fuel System Diagram:

CIRCUIT DESCRIPTION:

When the ignition switch is turned "ON," the electronic control module (ECM) will turn "ON" the in-tank fuel pump. It will remain "ON" as long as the engine is cranking or running, and the ECM is receiving reference pulses. If there are no reference pulses, the ECM will shut "OFF" the fuel pump in about 2 seconds after ignition "ON" or engine stops. The pump will deliver fuel to the fuel rail and injectors, then to the pressure regulator, where the system pressure is controlled to about 160-210 kPa (23.2-30.5 psi) depending on engine operating conditions. Excess fuel is then returned to the fuel tank.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

5. Pressure below 160 kPa (23.2 psi) may cause a lean condition. It could also cause hard starting cold and poor driveability. Low enough pressure will cause the engine not to run at all. Restricted flow may allow the engine to run at idle, or low speeds but may cause a surge and stall when more fuel is required, as when accelerating or driving at high speeds.

6. Restricting the fuel return line allows the fuel pump to develop its maximum pressure (dead head pressure). When B+, 12 volts is applied to the pump test terminal, pressure should be above 210 kPa (30.5 psi).

7. This test determines if the high fuel pressure is due to a restricted fuel return line or a pressure regulator problem.